The sweetpotato (Ipomoea batatas) is a member of the morning glory family, Convolvulaceae. Sweetpotatoes produce an edible storage root that is developmentally and anatomically derived from root tissue. This contrasts with potatoes (Solanum tuberosum), which produce an edible tuber that is derived from an underground stolon and is similar in structure to an above-ground stem. New plantings of sweetpotato are commonly produced via two methods (1) vegetative stem cuttings taken from plants in the field or greenhouse, and (2) cuttings of sprouts (i.e. small plants) that arise from adventitious buds (i.e. buds that are not derived from meristematic tissue) produced from storage roots that have been planted in soil in three to five foot wide “plant beds” in the spring. These sprouts are cut and planted in the field using a mechanical transplanter. In contrast, potatoes are typically propagated from cut or whole tubers planted directly into the soil. New plants arising from the seed tubers are derived from the eye of the potato tuber, with each eye being equivalent to a stem node and consisting of a raised or depressed ridge or protuberance, bearing a scale-like leaf subtending a minute meristematic bud in its center and flanked by two leaf primordia.
The color of the flesh of the sweetpotato root varies with the cultivar and can range from white to orange to purple. Presently, the dominant sweetpotato variety produced in the United States is ‘Beauregard’ (unpatented). The present invention, a new and distinct sweetpotato variety named ‘Covington’, provides an improvement over ‘Beauregard’ in that it generally produces shorter and more uniformly shaped storage roots than ‘Beauregard’ and it appears to be less sensitive to genotype by environmental interactions, which is perceived to be a major flaw in ‘Beauregard’. ‘Covington’ also typically scores as well as or better than ‘Beauregard’ in the flavor of its baked storage roots as measured by standardized and informal taste panels.
Lineage. ‘Covington’ originated from botanical seed harvested from the sweetpotato clone NC1528. NC1528 produces a vigorous vine similar to that of ‘Covington’. A distinguishing feature of the vine of NC1528 is that it possesses leaf nodes that typically have purple pigmentation (187B); whereas, the internodes of ‘Covington’ do not. NC1528 also produces tan-orange to cream-orange colored storage roots (22C to 22D) with medium orange flesh (28B to 28C); whereas, the storage roots of ‘Covington’ are light to medium rose-colored (33D to 34D) that possess a similar flesh color (28B to 28C).
NC1528 was one of 26 genotypes present in the North Carolina State University (NCSU) Sweetpotato Breeding and Genetics Program's 1997 open-pollinated polycross Streptomyces soil rot (SSR) breeding nursery. The SSR breeding nursery was planted at the North Carolina Department of Agriculture and Consumer Service's (NCDA&CS) Central Crops Research Station in Clayton, Johnston County, North Carolina. The 26 genotypes present in the SSR breeding nursery were randomly mated; therefore, the male parent of ‘Covington’ is unknown. Seedlings from the SSR breeding nursery were planted in the NCSU Horticultural Sciences greenhouses in March of 1998. A single cutting was taken from each seedling and planted in the field in May of 1998 in an “on-farm” trial and selected as a “single-hill selection” on Sep. 9, 1998. A “single-hill selection” includes the storage roots derived from the single plant cutting, typically ranging from 2 to 15 storage roots with 2 to 10 storage roots from selected hills being saved for plant propagation the following year.
The “on-farm” trial was conducted in Green County near Kinston, N.C. ‘Covington’ was vegetatively increased, evaluated and advanced as the clone NC98-608; the “98” referring to the year in which ‘Covington’ was selected as a “single-hill” and the “608” indicating that the ‘Covington’ selection was the 608th “single-hill selection” made by the breeding program in 1998. Covington was first recognized as being potentially superior to ‘Beauregard’ after two further cycles of increase, and field and disease resistance evaluations at the NCDA&CS Horticultural Crops Research Station (HCRS), Clinton, N.C. and the NCSU Cunningham Research Station, Kinston, N.C. during 1999 and 2000.
Asexual Reproduction. ‘Covington’ has been asexually propagated via vegetative cuttings and/or storage root derived sprouts since its original selection in September 1998. Storage and plant bed propagation of the sweetpotatoes for sprout production was done at the NCDA&CS Horticultural Crops Research Station, Clinton, N.C. After two additional cycles of field selection as the clone NC98-608, ‘Covington’ was submitted to the NCSU Micropropagation Unit in order to eliminate viruses and pathogens via mericulture clean-up, and for subsequent tissue culture entry. The combination of characteristics disclosed herein for ‘Covington’ has remained stable, and the plant reproduces true-to-type through successive generations of asexual reproduction.